Evaluate $13-0.75w+8x$ when $w=12$ and $x=\dfrac12$.
Explanation: Let's substitute $ w= {12}$ and $ x={\dfrac12}$ into the expression. $\phantom{=}13-0.75 {w} +8{x}$ $=13-0.75( {12}) +8\left({\dfrac12}\right)$ $=13-9+4$ $=8$